JP3297027B2 - High strength and high ductility α + β type titanium alloy - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-strength titanium alloy having high strength and excellent weldability (meaning the ductility of a weld heat affected zone: the same applies hereinafter), good ductility, and capable of producing coils. It is.

[0002]

2. Description of the Related Art Titanium alloys are lightweight, strong, tough,
Due to its excellent corrosion resistance, it has recently been widely used in the fields of the aerospace industry, the chemical industry, and the like. However, titanium alloys are inherently poor workable materials, and therefore have a major drawback in that the cost for forming is very high compared to other materials. For example, typical α
Ti-6Al-4V alloy, which is a + β-type titanium alloy, is a difficult-to-work material and has poor cold workability, and it is virtually impossible to form a coil by cold working.

[0003] When a Ti-6Al-4V alloy is processed into a plate shape, a technique called pack rolling is adopted. That is, pack rolling refers to Ti obtained by hot rolling.
This is a method in which -6Al-4V alloy sheets are stacked in layers and placed in a mild steel box, and a thin sheet is manufactured by hot rolling while keeping the temperature below a predetermined temperature. In this method, a pack is manufactured. In addition to the need for mild steel cover and pack welding to perform welding, a release agent must be applied to prevent diffusion bonding between titanium alloy plates, and the work is extremely complicated and costly compared to cold rolling. In addition, the temperature range suitable for hot rolling is limited, so that there are many restrictions on processing.

On the other hand, Japanese Patent Application Laid-Open Nos. 3-274238 and 3-166350 disclose A in a titanium base material.
The contents of l, V and Mo are defined, and Fe, N
By containing at least one alloying element selected from i, Co, and Cr in an appropriate amount, the Ti-6Al-4
It is described that a titanium alloy having a strength comparable to that of a V alloy and being superior in superplastic workability and hot workability to a Ti-6Al-4V alloy can be obtained.

Further, Japanese Patent Application Laid-Open No. 7-54081 and
No. 54083 discloses an Al content of 1.0 to 4.5%.
And the V content is 1.5-4.5.
%, The Mo content is regulated to 0.1 to 2.5%, or by further containing a small amount of Fe or Ni, the cold workability is enhanced while maintaining high strength, and further, the weldability (particularly, There is disclosed a titanium alloy having an increased strength of the heat affected zone.

[0006] This titanium alloy is considered to be excellent in that it has both cold workability and high strength and also has improved weldability. However, in these inventions, since it is necessary to ensure excellent cold workability, since the deformation resistance at the time of plastic working is suppressed, the strength is considerably low, and even though the strength is high, 0.2% after annealing. 784MPa (80kgf)
/ Mm ² ) level is the limit, and if the strength is further increased, the cold workability is reduced, so that coil production is almost impossible.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above situation, and its object is to provide α +
It is intended for β-type titanium alloys and has excellent strength properties and cold workability. Specifically, it has a resistance of 813% with a 0.2% proof stress after annealing.
MPa (83kgf / mm ² ) or more, 882M in tensile strength
An object of the present invention is to provide an α + β-type titanium alloy having a Pa (90 kgf / mm ² ) or more, a critical cold rolling reduction of about 40% or more, and a ductility capable of producing a coil.

[0008]

The high-strength and high-ductility α + β-type titanium alloy according to the present invention, which can solve the above-mentioned problems, is characterized in that at least one kind of the all-solution solid-solution β-stabilizing element is M
o 2.0 to 4.5% by mass (hereinafter referred to as% by mass unless otherwise specified), at least one of the eutectoid β-stabilizing elements
The seed contains 0.3 to 2.0% by Fe equivalent and further comprises Si:
0.1-1.5% by mass, and C: 0.01-0.15
% By weight and an Al equivalent of more than 3% by weight 5.5
Mass% or less, and a critical cold rolling reduction of 40% or more.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION As described above, the α + β type titanium alloy of the present invention is defined as the α-stabilizing element in which the contents of the solid solution β-stabilizing element and the eutectoid β-stabilizing element are specified. The base composition is an α + β-type titanium alloy having a preferable Al equivalent including Al and having an appropriate amount of Si and C, thereby providing excellent strength characteristics and cold workability, and having high strength. It has good ductility and enables coil production, and the reason for defining the content ratio of each of the above constituent elements will be clarified below.

[0010] At least one of the total solid solution type β stabilizing elements
Species: Mo-equivalent 2.0 to 4.5% Mo, for example, is a solid solution type β-stabilizing element that increases the volume ratio of the β-phase and dissolves in the β-phase to contribute to an increase in strength. In addition, it has the property of forming a fine equiaxed crystal structure by forming a solid solution in a titanium base material, and is a useful element from the viewpoint of improving the balance between strength and ductility. In order to effectively exert the effect of the solid solution type β stabilizing element, the content should be 2.0% or more, more preferably 2.5% or more. However, if it is too much, the ductility decreases after β annealing. In addition, the corrosion resistance of the titanium alloy increases, and it becomes difficult to remove the oxide scale generated during annealing after cold rolling and the base metal in which oxygen, which is referred to as α-case, is dissolved. Since the density of the entire alloy is increased and the characteristic of the titanium alloy inherently having high specific strength is impaired, it should be suppressed to 4.5% or less, more preferably 3.5% or less.

The most typical solid solution type β-stabilizing element is Mo, but V, Ta, Nb and the like have the same effect as Mo. Is expressed as Mo equivalent including these [Mo + 1 / 1.5
[V + 1 / 5.Ta + 1 / 3.6.Nb] should be adjusted in the range of 2.0 to 4.5%.

At least one of the eutectoid β-stabilizing elements: F
An eutectoid β-stabilizing element such as 0.3 to 2.0% Fe in e equivalent has an effect of improving the hot workability in addition to increasing the strength by adding a small amount. Although the reasons have not been clarified at this time, Mo and F
When e coexists, cold workability is enhanced. In order to effectively exhibit such an effect, Fe should be contained at 0.3% or more, more preferably 0.4% or more. However, if the Fe content is too large, the ductility after β annealing is greatly reduced, and segregation during the production of an ingot becomes remarkable, causing quality stability to be impaired.
It should be kept below, more preferably below 1.5%.

Since Cr, Ni, Co, etc. have the same effect as such Fe, when Cr is contained, the Fe equivalent including these is [Fe + 1 / 2.Cr + 1/2.
Ni + 1 / 1.5.Co + 1 / 1.5.Mn] is 0.3 to 2.0%
Must be adjusted to be within the range.

Al equivalent: more than 3% to 5.5% or less Al is an element that contributes to strength improvement as an α-stabilizing element. If the Al content is 3% or less, the titanium alloy becomes insufficient in strength. However, when the Al content is 5.5% or more, not only does the limiting cold rolling rate decrease, making coiling difficult, but also the cold workability as a coil product decreases, and until the product is rolled to a predetermined thickness. The number of times of cold rolling and annealing increases, leading to an increase in cost. Considering the balance between strength and cold workability, a more preferable lower limit of the Al equivalent is 3.5%.

In the present invention, Sn and Zr also exert an action as an α-stabilizing element in the same manner as Al. Therefore, when these elements are contained, they are included in the Al equivalent weight. [Al + 1/3 ・ Sn + 1/6 ・ Z
r] should be adjusted to be in the range of more than 3% and 5.5% or less.

Representative examples of preferable α + β type titanium alloys satisfying the requirements of the above component composition used as the base titanium alloy in the present invention include Ti- (4-5%) Al- (1.5-3
%) Mo- (1-2%) V- (0.3-2.0%) Fe (particularly Ti-4.
5% Al-2% Mo-1.6% V-0.5% Fe).

Si: 0.1-1.5% Above all solid solution type β
Α + β-type titanium alloy having a base composition that satisfies the stabilizing element and the eutectoid β-stabilizing element, and further, the content requirement of Al equivalent,
It has excellent cold workability with a critical cold rolling reduction of about 40% or more and can be made into a coil. However, strength properties and weldability are not always sufficient. Can not respond.

However, when 0.1 to 1.5% of Si is contained in the α + β type titanium alloy having the above base composition, the strength characteristics and welding heat as a titanium alloy can be obtained without reducing the ductility required for coiling. It was confirmed that the characteristics (strength and ductility) of the affected area could be significantly improved.

That is, Si has the effect of increasing the strength characteristics without substantially affecting the cold rolling properties of the α + β type titanium alloy, and also exhibits the effect of increasing the strength and ductility of the weld heat affected zone. By adding an appropriate amount of Si, the strength and ductility of the titanium alloy base material can be further improved, and a weld heat affected zone exhibiting a high level of strength and ductility can be obtained.

In order to exert such an effect of Si more effectively, it is necessary to contain Si in a very limited range of 0.1 to 1.5%, and the Si content is insufficient. In this case, the strength tends to be insufficient, and the effect of improving the strength-ductility balance of the welded portion is also insufficient. Conversely, if it exceeds 1.5%, the cold-rolling property is poor and the coil production becomes difficult. The lower limit of Si is more preferably 0.2%, and the upper limit is more preferably 1.0% in consideration of the advantages and disadvantages of Si.

C: 0.01 to 0.15% C has the effect of further improving the strength characteristics while maintaining the excellent ductility of the α + β type titanium alloy, and slightly reduces the ductility of the weld heat affected zone. However, the effect of adding C further increases the strength and ductility of the titanium alloy base material, and can further increase the strength and ductility of the weld heat affected zone.

In order to exert such an effect of C more effectively, C must be contained in a very limited range of 0.01 to 0.15% or less, and the content of C is insufficient. If it exceeds 0.15%, on the contrary, if it exceeds 0.15%, remarkable precipitation hardening of a carbide such as TiC impairs the cold-rolling property and hinders coil rolling. Such C
The lower limit of C, which is more preferable in consideration of the interest and loss of
The upper limit is 2%, and a more preferred upper limit is 0.12%.

In the present invention, it is preferable to include a small amount of O (oxygen) in addition to the above Si and C, since the strength can be further increased without substantially adversely affecting the coiling and ductility of the titanium alloy. . Such an effect of oxygen is exerted in a very small amount, but in order to exert the effect more reliably, about 0.07% or more, more preferably 0.1% or more.
It is preferable to contain about 1% or more. However, when the oxygen content is too large, the cold workability is reduced, and the ductility is also reduced due to an excessive increase in strength. Therefore, the oxygen content is 0.25% or less, more preferably 0.18% or less. Should be kept to a minimum.

In the present invention, the aforementioned α + β
It is not always clear why the above-mentioned effects are exerted by incorporating appropriate amounts of Si and C, and furthermore, an appropriate amount of oxygen into the titanium alloy. However, the following is considered. Can be

That is, the reason why the strength properties can be improved without impairing the cold-rolling property by incorporating an appropriate amount of Si is that although Si is dissolved in the β phase and contributes to the strength improvement, It does not become a major inhibitory factor, and even if Si is contained beyond the solid solubility limit, the formation of silicide keeps the Si concentration in the β phase below a certain level. Therefore, it is considered that if the Si content is suppressed within a range in which ductility is not hindered by excessive silicide generation, strength characteristics can be improved while maintaining high ductility.

When an appropriate amount of Si is contained, coarsening of the crystal structure in the heat affected zone by welding is suppressed by the silicide generated in the β phase as described above, and Ti is trapped by the precipitation of the silicide to form the β phase. It is thought that the residual β phase increases due to the stabilization of the dissolution or the transformation inhibiting action of the solid solution Si, and these effects are combined to improve the weldability.

C also forms a solid solution in the α phase and contributes to the improvement of the strength, but does not significantly affect the ductility of the α phase. Moreover, even when C exceeding the solid solubility limit is contained, the C concentration in the α phase is maintained at a certain fixed value or less due to the formation of carbide. Therefore, it is considered that if the C content is suppressed within a range in which ductility is not impaired by excessive carbide generation, strength properties can be enhanced while maintaining high ductility.

Note that Si and C exert an effect of increasing the heat resistance of the Ti alloy in addition to the above-mentioned effects.

Further, O forms a solid solution in both the α phase and the β phase (the solid solution itself is larger in the α phase) to exert a solid solution strengthening action. If the content increases, the ductility is impaired. Therefore, the content should be kept to an extremely small amount as described above.

The titanium alloy of the present invention may inevitably contain elements other than those described above. However, as long as the properties of the alloy of the present invention are not impaired, the inclusion of trace amounts of these elements is permissible. Further, in order to provide still other characteristics while maintaining the above characteristics of the present invention, it is possible to positively contain elements other than those described above. Platinum group elements (Pb, Ru, Ir, In, etc.) having an effect of improving corrosion resistance as such acceptable active addition elements: preferably 0.03 to
P having an effect of improving heat resistance (preferably about 0.05% or less), N having an effect of improving strength (preferably about 0.03% or less), and the like.

The α + β-type titanium alloy of the present invention, whose constituent elements are specified as described above, is a solid-solution β-stabilizing element and a eutectoid-type β-stabilizing element, and furthermore, an α + β-type titanium having a specified Al equivalent. By using an alloy as a basic composition, containing an appropriate amount of Si and C, or further containing an appropriate amount of O, it has excellent ductility that enables coil production while having a high level of strength characteristics, Has excellent properties in terms of weldability. Specifically, the 0.2% proof stress after annealing in the α + β temperature range is 813 MPa (83 kgf / m2).
m ² ) or more, and the tensile strength is 882 MPa (90 kgf / m
m ² ) or more and a critical cold rolling reduction of 40% or more.

In the case of an α + β type titanium alloy having a critical cold rolling reduction of less than 40%, if the coil is manufactured by a continuous method, the number of repetitions of cold rolling and annealing increases, so that the cost is reduced. Not only does it not fit the actual situation, but also it is difficult to obtain a recrystallized structure,
Problems such as anisotropy in the L direction increase.
However, when the critical cold rolling rate is 40% or more, the coil can be manufactured by the continuous method without any trouble, and the cost can be significantly reduced by improving the productivity.

Here, from the industrial viewpoint, the critical cold rolling rate means that even if a slight crack occurs, the crack is reduced to a certain extent (for example, about 5 mm) from the stage where the growth is stopped, to the sheet surface. It refers to the rate of thickness reduction at the limit at which development begins.

The upstream processing conditions up to cold rolling using the α + β type titanium alloy of the present invention are not particularly limited, but are generally performed under the following conditions. That is, the ingot is divided (forged or rolled) at a transformation temperature or higher to obtain a rolled slab. At this time, if it is necessary to make the macrostructure fine, two or more lumps are intentionally performed until the final slab is obtained.
It may be done more than once. Next, the obtained hot-rolled slab is heated to an α + β temperature range below the transformation temperature (usually, [β transformation point−30] ± 20 ° C.) and hot-rolled, and then a temperature range from 700 ° C. to the transformation temperature or lower. (However, 850
(It is better to avoid around ℃.), And descaling is performed to obtain a hot-rolled material. The cold rolling using the hot-rolled material is performed by repeating the operation of annealing in a temperature range of 700 ° C. to the transformation temperature or less (however, it is better to avoid around 850 ° C.) with a draft of about 40% as a guide. Obtain a predetermined thickness.

In order to obtain a coil by cold rolling,
It is desirable to have excellent hot ductility assuming that it is wound around a hot coil, and to be less likely to cause internal cracks and ear cracks due to a temperature drop. However, in the present invention, as described above, an appropriate amount of Si
In addition to containing C and C, the amount of β-stabilizing elements is reduced, and the β transformation temperature is sufficiently increased, so that the hot workability when wound around a hot coil at a temperature lower than the transformation temperature is also excellent.
In order to form an equiaxed structure, hot rolling at a temperature not higher than the β transformation point is generally required. From the viewpoint of hot workability,
The β transformation point is desirably 900 ° C. or higher, more preferably 950 ° C. or higher.

In the present invention, as described above, α
+ Base alloy of β-type titanium alloy
And C content, preferably O content, can provide excellent cold rollability for coil production while maintaining a high level of strength properties. After further study on the requirements to more reliably guarantee the strength characteristics of the part,
When the relationship between the 0.2% proof stress (YS) and the elongation (El) after annealing in the temperature range satisfies the relationship of the following formula (1), the strength-elongation balance of the weld heat affected zone is good. It was confirmed that high weldability was exhibited stably. This point will be described in detail in a later embodiment with reference to FIG.

6.9 × (YS-85.2) + 25 × (El−8.2) ≧ 0 (1) As described above, the α + β type titanium alloy of the present invention has a conventional Ti having a critical cold rolling reduction of about 40% or more. -6Al-4V alloy has excellent cold-rolling properties not found in alloys and the like, so that it is possible to manufacture coils that were hardly possible in the past, and to perform various shapes by cold working, for example, thin sheets and waves. Board,
It can be easily processed into a pipe shape.

At this time, depending on the type of the cold-worked product, it may be necessary to perform rolling beyond the above-mentioned limit cold rolling reduction. In this case, one or more softening annealings are performed during the cold rolling. The treatment may be performed and cold rolling may be performed to an arbitrary thickness while relaxing work hardening. In any case, since the titanium alloy of the present invention has a high critical cold rolling reduction of about 40% or more, it is processed into an arbitrary thickness and shape only by cold rolling without the need for pack rolling as described above. can do.

The conditions of the annealing performed during the cold working as necessary are not particularly limited, but usually, (T _b -300 ° C.) to (T _b -25 ° C.) based on β transus (T _b ). And a condition of about 3 to 120 minutes is adopted.

As described above, the α + β type titanium alloy obtained by performing such an annealing treatment has a 0.2% proof stress at room temperature after annealing in the α + β temperature range of 813MP.
a (83 kgf / mm ² ) or more and tensile strength of 882M
It exhibits excellent physical properties not found in conventional titanium alloys, because it exhibits a Pa (90 kgf / mm ² ) or more and has a good balance between strength and ductility of the weld heat affected zone after welding. Will have.

The α + β type titanium alloy of the present invention thus obtained can be used for coil production by utilizing its excellent cold workability.
It can be easily processed into any shape such as a tube. In addition, because it has both excellent strength properties and ductility as described above, and has good weldability and the weld heat affected zone exhibits a high level of ductility, applications where welding is performed before processing into a final product,
For example, plate materials for heat exchangers, Ti golf head materials, welded pipes, various wires, rods, ultrafine wires, aircraft parts,
It can be used widely and effectively as mountain climbing equipment, fishing gear, and other superplastic molding materials and various composite materials.

[0042]

EXAMPLES Hereinafter, the structure and operation and effect of the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples, and the present invention is applicable to the above and following points. The present invention can be appropriately modified and implemented within the scope of the invention, and all of them are included in the technical scope of the present invention.

Example 1 An ingot of a titanium alloy having the composition shown in Table 1 (60 × 130 ×
260 mm) by induct skull dissolution and then β
After being heated to a temperature range (about 1100 ° C.) and then subjected to slab rolling to a plate having a thickness of 40 mm, it is kept at a β temperature range (about 1100 ° C.) for 30 minutes and then air-cooled. Subsequently, hot rolling was performed by heating in an α + β region (900 to 920 ° C) below the β transformation point to produce a hot-rolled sheet having a thickness of 4.5 mm. Then, after annealing again in the α + β region (about 760 ° C.) for 30 minutes, the 0.2% proof stress, tensile strength, and elongation were measured. In addition, the test piece machined the surface of the test plate and processed the gauge length to 50 mm and the width of the parallel portion to 12.5 mm.

Next, a shot blast treatment and pickling were performed to remove an oxide layer on the surface, and then the tensile properties were evaluated. Using this as a cold-rolled material, the rolling amount was reduced to about 0.2 mm per pass, and cold-rolling was continued until a sheet surface crack occurred to evaluate the cold-rolling property. Further, in order to evaluate the weldability, each test material was heated at 1000 ° C., which is equal to or higher than Tβ, for 5 minutes and then air-cooled, and the tensile properties of the needle-like structure were examined.

The results are collectively shown in Table 2.

[0046]

[Table 1]

[0047]

[Table 2]

FIG. 1 shows the experimental data shown in Table 1 above showing the values of 0.2% after β annealing corresponding to the physical properties of the heat affected zone.
It is a graph showing the relationship between 2% proof stress and elongation.

In this graph, the solid line Y shows the relationship between the 0.2% proof stress and the elongation of the comparative materials other than those having a cold rollability other than x (the critical cold rolling reduction is less than 40%). X is [6.9 × (YS-85.2) + 25 × (El-8.2)]
Represents a relational expression represented by.

As is clear from this graph, the solid line Y and the chain line X have a 0.2% proof stress of 813 MPa (83 kgf /
mm ² ), the slope of the solid line Y (comparative material) in the region where the proof stress is higher than the proof stress is steeper than the dashed line X. It can be confirmed that the elongation rate sharply decreases with the rise of. On the other hand, in the example of the present invention, the relationship between the proof stress and the elongation rate is located on the upper right side of the chain line X, and the decrease in the elongation rate with the increase in the proof stress is relatively small.
It can be confirmed that the material has high strength and high ductility.

FIG. 2 is a graph showing the relationship between the 0.2% proof stress after α + β annealing and the elongation rate. The graph shows the relationship between the proof stress of 813 MPa (83 kgf / mm ² ). In contrast, none of the comparative materials reached the above-mentioned proof stress, whereas all of the example materials showed a higher proof stress, and from this graph, the material of the present invention has high strength and excellent ductility. You can see that it is.

Embodiment 2 The titanium alloy (Ti-2Mo-1.6
V-0.5Fe-4.5Al-0.3Si-0.03C) and a titanium alloy (Ti-2Mo-1.6V-0.5Fe-4.5Al-) added with 0.05% of a platinum group element Ru as a corrosion resistance improving element. 0.3Si-0.03C-0.05R
u) and a Ti-6Al-4V alloy as a conventional product, and these were subjected to slab rolling → hot rolling →
Annealing is performed sequentially, and wet polishing (# 40
0) and the cold rolled material obtained by performing the degreasing treatment,
The cold rolling property, strength and weldability were examined in the same manner as in Example 1, and crevice corrosion resistance (100 ° C. in 20% NaCl aqueous solution).
For one week).

The results are as shown in Table 3 below.
The material of the present invention is inferior in crevice corrosion resistance as compared with the conventional material of the symbol Z, but the material of the present invention of the symbol Y to which a trace amount of Ru is added as a platinum group element has an excellent cold rolling property of the symbol X, It can be seen that excellent crevice corrosion resistance is exhibited while maintaining strength and weldability.

[0054]

[Table 3]

[0055]

The present invention is constituted as described above, and is based on an α + β-type Ti alloy in which the contents of the total solid solution type β-stabilizing element and the content of the eutectoid type β-stabilizing element are defined, By containing specific amounts of Si and C or a small amount of oxygen, it has strength characteristics not inferior to Ti-6Al-4V alloy, which is the most widely used titanium alloy. Titanium alloy, which has all of the formability, strength and weldability while significantly improving the cold workability lacking in the alloy and enabling coil rolling, and significantly improving the strength and ductility of the weld heat affected zone. Can be provided.

Therefore, the titanium alloy of the present invention can be widely used in various applications by utilizing its features. In particular, by taking advantage of its excellent corrosion resistance, light weight, and electrothermal properties, and utilizing its excellent cold rolling property. For example, it can be used very effectively as a plate material for a heat exchanger.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between 0.2% proof stress and elongation after annealing in a β temperature range (corresponding to a welding heat affected zone).

FIG. 2 is a graph showing the relationship between 0.2% proof stress and elongation after annealing in an α + β temperature range.

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-2-301536 (JP, A) JP-A-4-202729 (JP, A) JP-A-8-120373 (JP, A) JP-A-9-1997 31572 (JP, A) JP-A-7-54083 (JP, A) JP-A-3-274238 (JP, A) JP-A-1-242743 (JP, A) JP-B-51-17489 (JP, B2) (58) Field surveyed (Int. Cl. ⁷ , DB name) C22C 1/00-49/14

Claims (3)

(57) [Claims] At least one of the total solid-solution β-stabilizing elements
The seed contains 2.0 to 4.5% by mass of Mo equivalent, at least one of the eutectoid β stabilizing elements contains 0.3 to 2.0% by mass of Fe equivalent, and further contains Si: 0.1 to 1 %. 0.5% by mass, and
C: contains 0.01 to 0.15% by mass and Al
A high-strength and high-ductility α + β-type titanium alloy having an equivalent weight of more than 3% by mass and 5.5% by mass or less . 2. The method according to claim 1, wherein the coil can be manufactured.
High-strength and high-ductility α + β-type titanium alloy described in 1. 3. The 0.2% proof stress after annealing in the α + β temperature range.
3 is 813 MPa or more.
High strength and high ductility α + β type titanium alloy.